Yeah, I honestly have no idea. Ryan/Esposito is where my heart lies, and I'm probably never going to be able to get away from the pairing entirely. But I posted a Hawaii Five-0 fic a while back and got a huge amount of response on it. I think it really is a per-fandom thing. The longer a show is around, the less enthusiasm there is in general maybe? There was a lot more feedback for Castle once upon a time, or at least for my little neck of the fandom. But the characters I favor are supporting characters in a show heavily focused on the hook-up-already shenanigans of the leading pair, in a fandom heavily biased toward het.

Plus, in canon, one of half of the pairing has been married off in a weak side plot (to a character played by the actors RL wife...ugh) and the other has been shuffled into an equally weak will-they-or-won't-they (though really should they?) romantic subplot where they're dubiously paired with another acceptably ethnic supporting character...I'm convinced simply because she was there.